1. Field of the Invention
Embodiments disclosed herein generally relate to a magnetic read head for use in a hard disk drive.
2. Description of the Related Art
At the heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent to a media facing surface (MFS), such as an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions corresponding to host data. The read and write heads are connected to a signal processing circuitry that operates according to a computer program to implement the writing and reading functions.
Modern HDDs use tunnel magneto resistance (TMR) read heads. The TMR read head uses magnetic tunnel junctions for sensing magnetically written data on a HDD. The direction of magnetization for a ferromagnetic “free layer” can be switched by an external magnetic field. If the magnetization is in a parallel orientation to a second pinned ferromagnetic film, it is more likely that electrons will tunnel through the insulating film separating them than if they are in an anti-parallel orientation. Consequently, such a junction can be switched between two states of electrical resistance, one with low and one with very high resistance.
The need for ever increased data density is pushing researchers to develop data recording systems that can read and record ever smaller bit lengths in order to increase the density of data recorded on a magnetic medium. The size of a reader gap thickness in the read head is related to the size of the bit length the read head can sense. This has led to a push to decrease the reader gap thickness for the read heads. However, the amount by which the reader gap thickness can be decreased has been limited by physical limitations of sensors and also by the limitations of currently available manufacturing methods.
Future read heads for high density media require a very narrow reader gap. The reader gaps for conventional TMR/CPP read heads cannot meet the requirements for future high density media simply by thinning the functional layers of the read head. Recently, alternative read head structures, such as recessed pinned layers and scissor sensors, have been the focus of development for narrowing the reader gap of the read heads.
The conventional read heads using recessed pinned layers have been considered with various configurations of the pinned layer recessed back from the MFS. As a result, the size of the reader gap can be shrunk approximately 7 nm to about 18 nm. However, aside from fabrication challenges, the reduction in the pinning energy and the stability of the pinned layer at the MFS has been problematic for read heads using the recessed pinned layers.
Read heads using the scissor sensor structure has been developed for many years. Using this technology, the reader gap can be reduced approximately 10 nm to about 14 nm. However, a great challenge related to yield and the sensor stability still remains.
Therefore, there is a need to further reduce the reader gap while still preserving the stability and reliability of the magnetic read head sensor.